Abstract: A pool of echo cancellers provides echo cancellation on PCM digital transmissions on an as needed basis. A dynamic port device operating under the direction of call processing identifies the transmissions requiring echo cancellation and routes the identified transmissions through echo cancellers. The echo cancellation can be performed on an as needed basis without having to dedicate an echo canceller to each DS0 channel. The dynamic port device can provide multiplexing up to SONET carrier levels immediately following selective echo cancellation.